The invention relates to power-driven conveyors and more particularly to motorized rollers.
Motorized rollers are commonly used to propel a series of conveyor rollers or conveyor belts. As shown in FIGS. 1a and 1b, motorized rollers 20 typically include an electric motor 22 whose output shaft 24 is coupled to a reduction gear 26 that drives an outer cylindrical shell 28. The motor 22 and the reduction gear 26 are housed inside the hollow cylindrical shell 28. Stationary end shafts 30 extend out from end caps 32 for mounting the motorized roller 20 to the side walls of a conveyor. At least one of the stationary shafts 30 can be hollow to admit power and control cables 34 to the motor 22. The outer cylindrical shell 28 rotates about an axis of rotation 36 coincident with the shafts 24, 30. The shell 28 can directly drive a tensioned conveyor belt; it can propel articles directly and drive other idle rollers to drive articles via one or more transmission belts; or it can have or be outfitted with lagging that has drive surfaces to positively drive a toothed belt.
Motorized rollers are generally small in diameter so that they can be closely spaced in a powered roller conveyor. But the small outside diameter of motorized rollers limits the size of the internal electric motor and the maximum torque available for a given roller speed.